Seokheun Choi, assistant professor of Electrical and Computer Engineering in the Watson School of Engineering and Applied Sciences, photographed, November 1, 2012.

Answer: Generally speaking, bio-fuel is an alternative or additive to standard car fuel. Just like standard fuel, biofuels work and burn as a result of internal combustion in car engines. This is what powers vehicles and makes them run. To use biofuel in car engines, you don't need to make major modifications on your car engine because this type of fuel works practically in the same way as standard car fuel. A biofuel car can use 100% biofuel sources to power a car engine or it can be combined with regular petroleum to create a biofuel blend.

Biofuel is most commonly defined as a renewable source of energy, which is produced from biological material or biomass, such as animal fats, sugar cane, corn, cellulose or vegetable oils. The most widely spread types of biofuel for vehicles are bioethanol and biodiesel. Both forms of biofuel have definite environmental advantages over petroleum-based gasoline and diesel fuel.

First of all, bioethanol is an alcohol product produced from corn, potatoes, wheat and even biomass. When combined with gasoline, it increases octane levels, while also promoting more complete fuel burning that reduces harmful emissions such as carbon monoxide. Bioethanol is also non-toxic, water soluble and quickly biodegradable. On the other hand, biodiesel is a domestic, renewable fuel for diesel engines derived from natural oils. But you can't just use straight animal fats or vegetable oils as fuel. They have to undergo a chemical reaction, in which the fat or oil is purified and reacted with alcohol to form esters and glycerol. The end product can be used alone or mixed with regular petroleum diesel.

However, there are still some disadvantages to using this type of biofuel sources. One of the biggest disadvantages is cost. Biodiesel is more expensive than petroleum-based fuel to produce, as it uses renewable fats and oils by growing the vegetables and feeding the animals. Another disadvantage is that a biodiesel converter needs to be installed in your car engine in order to reduce the biodiesel's viscosity before it reaches the engine injector, where fuel is delivered and burned to produce power to make the vehicle run. Also, bioethanol does not have a very high energy density.

In summary, despite some negative characteristic of biofuels, production is increasing throughout the world and it currently supplies 3 percent of the world's fuel needs. Driven by increasing concerns over the oil depletion/energy-climate crisis/environment pollution, biofuels will be a major focus for renewable energy production in the future.